\(\left(x+5\right)\left(x+2\right)-3\left(4x-3\right)=\left(5-x\right)^2\)
\(\Leftrightarrow x^2+5x+2x+10-12x+9=25-10x+x^2\)
\(\Leftrightarrow x^2-x^2+5x+2x-12x+10x=25-10-9\)
\(\Leftrightarrow5x=6\Leftrightarrow x=\frac{6}{5}\)
Vậy S = \(\left\{\frac{6}{5}\right\}\)